The use of dipropylenglycol or diethylenglycol ditolutes or dibenzotes and their compounds, and their use as plasticizers is documented in technical literature since the last century. For example, the following publications describe the use as a plasticizer of diethylenglycol dibenzoate (DDB), triethylenglycol dibenzoate (TDB), diethylenglycol ditoluate (DDT), and triethylenglycol ditoluate (TDT) or their compounds: U.S. Pat. No. 2,070,331 (1936); UK 496,574 (1936); U.S. Pat. No. 2,585,448 (1948); UK 815,991 (1956); U.S. Pat. No. 2,956,978 (1960); UK 1,321,383 (1971); U.S. Pat. No. 3,874,985 (1973); Jpn Tokkyo Koho 81 00,304 (1975); A. V. Bailey et al., J. Am. Oil. Chem. Soc 1976, 53(5), 176–178; W. D. Arendt (Velsicol Chemical Corporation), Tech. Pap. 1979, 25, 410–412; U.S. Pat. Nos. 4,277,387 1981; 4,331,579 (1982); 4,336,166 (1982); 4,444,933 (1982); EPO 0 157 426 (1984); EPO 0 234 710 (1987); Fed. Regist. 1987 52(4) 527–530; U.S. Pat. Nos. 4,767,813 (1988); 4,818,779 (1989).
The plasticizer mentioned in a number of the above documents, since at least as early as 1982, is Benzoflex, trademark of Velsicol Chemical Corporation to denominate a range of plasticizers with a composition of DDB and TDB compounds. There are other trademarks using the same range of compounds or equivalents of the same polyglycol polyesters, such as K-Flex, owned by Furam Chemicals Ltd. The use as plasticizers of arylic diesters of other glycols, such as propylenglycol derivatives, is also described in literature.
There are two chemico-physical reasons:                1. a good plasticizer must be liquid at room temperature,        2. the polymer to be plasticized (such as vinyl or acrylic-type polymers) is water-repellent that recommend that the plasticizer should be a compound of arylic glycol diesters and, sometimes, triol triesters. In a document such as U.S. Pat. No. 5,676,742, when a compound with diethylenglycol and dipropylenglycol monoesters, together with the corresponding diesters, is described, it is to highlight that the advantage is not as a plasticizer, but as an additive resistant to the growth of mildew.        
The fact that the most popular plasticizers in industry are liquid diesters is because:                1. Processes in which a plasticizer is involved, are conducted in totally water-repellent mediums, such as poly(vinyl chloride) or poly(methyl acrylate). The nature of these water-repellent mediums means that the presence of monoesters deteriorates the technical properties of the plasticizer (for example, see U.S. Pat. No. 2,956,978).        2. The required flexibility in the final plastic is reduced if the plasticizers become solid at room temperature. A liquid compound of plasticizers in which at least one of its components of over 20% becomes solid at room temperature, has disadvantages in certain cases, such as when it is used with adhesives to join parts in motion.        
The highly water-repellent nature of the polymers to be plasticized means that the dispersability in water of these polymers is very short. This is demonstrated in recent generally vinyl or acrylic polymer-based industrial adhesives applied in aqueous mediums, as during industrial use of usual plasticized polymer formulae with DDB or TDB compounds, an aqueous phase and another water-repellent phase are quickly separated, rapidly causing a lack of homogeneity in these suspensions. This results in a faulty application of the adhesive leading to less adhesive power.